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Previous studies have revealed associations of meteorological factors with tuberculosis (TB) cases. However, few studies have examined their lag effects on TB cases. This study was aimed to analyse nonlinear lag effects of meteorological factors on the number of TB notifications in Hong Kong. Using a 22-year consecutive surveillance data in Hong Kong, we examined the association of monthly average temperature and relative humidity with temporal dynamics of the monthly number of TB notifications using a distributed lag nonlinear models combined with a Poisson regression. The relative risks (RRs) of TB notifications were >1.15 as monthly average temperatures were between 16.3 and 17.3 °C at lagged 13–15 months, reaching the peak risk of 1.18 (95% confidence interval (CI) 1.02–1.35) when it was 16.8 °C at lagged 14 months. The RRs of TB notifications were >1.05 as relative humidities of 60.0–63.6% at lagged 9–11 months expanded to 68.0–71.0% at lagged 12–17 months, reaching the highest risk of 1.06 (95% CI 1.01–1.11) when it was 69.0% at lagged 13 months. The nonlinear and delayed effects of average temperature and relative humidity on TB epidemic were identified, which may provide a practical reference for improving the TB warning system.
In recent years, the discovery of massive quasars at $z\sim7$ has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early Universe. Mounting observational and theoretical evidence indicates the viability of massive seeds, formed by the collapse of supermassive stars, as a progenitor model for such early, massive accreting black holes. Although considerable progress has been made in our theoretical understanding, many questions remain regarding how (and how often) such objects may form, how they live and die, and how next generation observatories may yield new insight into the origin of these primordial titans. This review focusses on our present understanding of this remarkable formation scenario, based on the discussions held at the Monash Prato Centre from November 20 to 24, 2017, during the workshop ‘Titans of the Early Universe: The Origin of the First Supermassive Black Holes’.
Formaldehyde (H2CO) and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Our recent single dish observation of formaldehyde and its deuterated species suggests that they form mostly on grain surfaces although some gas-phase contribution is expected at the warm HMPO stage. Since the single dish beam is larger, and since these high-mass star-forming regions are clustered and complex, it is however unclear whether the emission arises from the protostellar sources or from starless/pre-stellar cores associated with them. Therefore, interferometric observations are needed to separate the emission originating from the small and dense cores, to disentangle their formation routes and then being able to use them as powerful diagnostic tools of the physical and chemical properties of high-mass star forming regions.
Core-accretion theory predicts that the formation of giant planets predominantly occurs at the dense mid-plane of the inner ∼50 AU of protoplanetary disks. However, due to observational limitation, this critical region remains to be the least charted area in protoplanetary disks. With its great sensitivity, ALMA recently started to image optically thin line emissions arisen from the mid-plane of the inner 50AU in nearby disks, which unlocks an exciting new path to directly constrain the physical properties of the giant planet formation zone through gas tracers. Here we present the first spatially resolved observations of the 13C18O J=3-2 line emission in the TW Hya disk. We show that this emission is optically thin even inside the CO mid-plane snowline. Combining it with the C18O J=3-2 images and the previously detected HD J=1-0 flux, we directly constrain the mid-plane temperature and optical depths of the CO gas and dust. We report a mid-plane CO snowline at 20.5 ± 1.3 AU, a mid-plane temperature distribution of 27+4−3×(R/20.5AU)-0.47+0.06−0.07 K, and a gas mass distribution of 13+8−5×(R/20.5AU)-0.9+0.4−0.3 g cm−2 between 5-20.5 AU in the TW Hya protoplanetary disk. We find a total gas/mm-sized dust mass ratio of 140 ± 40 in this region, suggesting that ∼2.4 earth mass of dust aggregates have grown to > cm sizes (and perhaps much larger).
Vibrio cholerae O139 emerged as a causative agent of epidemic cholera in 1992 in India and Bangladesh, and was subsequently reported in China in 1993. The genetic relatedness and molecular characteristics of V. cholerae O139 in Guangdong Province, located in the southern coastal area of China, remains undetermined. In this study, we investigated 136 clinical V. cholerae O139 isolates from 1993 to 2013 in Guangdong. By conventional PCR, 123 (90·4%) isolates were positive for ctxB, ace and zot. Sequencing of the positive amplicons indicated 113 (91·7%) isolates possessed the El Tor allele of ctxB (genotype 3); seven carried the classical ctxB type (genotype 1) and three harboured a novel ctxB type (genotype 5). With respect to tcpA, 123 (90·4%) isolates were positive for the El Tor allele. In addition, pulsed-field gel electrophoresis (with NotI digestion) differentiated the isolates into clusters A and B. Cluster A contained seven of the non-toxigenic isolates from 1998 to 2000; another six non-toxigenic isolates (from 1998 and 2007) and all of the toxigenic isolates formed cluster B. Our results suggest that over a 20-year period, the predominant O139 clinical isolates have maintained a relatively tight clonal structure, although some genetic variance and shift has occurred. Our data highlight the persistence of toxigenic V. cholerae O139 in clinical settings in the southern coastal area of China.
We conducted a systematic review to compare resistance to third-generation cephalosporins (TGCs) in Shigella strains between Europe-America and Asia-Africa from 1998 to 2012 based on a literature search of computerized databases. In Asia-Africa, the prevalence of resistance of total and different subtypes to ceftriaxone, cefotaxime and ceftazidime increased markedly, with a total prevalence of resistance up to 14·2% [95% confidence interval (CI) 3·9–29·4], 22·6% (95% CI 4·8–48·6) and 6·2% (95% CI 3·8–9·1) during 2010–2012, respectively. By contrast, resistance rates to these TGCs in Europe-America remained relatively low – less than 1·0% during the 15 years. A noticeable finding was that certain countries both in Europe-America and Asia-Africa, had a rapid rising trend in the prevalence of resistance of S. sonnei, which even outnumbered S. flexneri in some periods. Moreover, comparison between countries showed that currently the most serious problem concerning resistance to these TGCs appeared in Vietnam, especially for ceftriaxone, China, especially for cefotaxime and Iran, especially for ceftazidime. These data suggest that monitoring of the drug resistance of Shigella strains should be strengthened and that rational use of antibiotics is required.
Electron microscopy (EM), cryo-electron microscopy (cryo-EM), and cryo-electron tomography (cryo-ET) are essential techniques used for characterizing basic virus morphology and determining the three-dimensional structure of viruses. Enveloped viruses, which contain an outer lipoprotein coat, constitute the largest group of pathogenic viruses to humans. The purification of enveloped viruses from cell culture presents certain challenges. Specifically, the inclusion of host-membrane-derived vesicles, the complete destruction of the viruses, and the disruption of the internal architecture of individual virus particles. Here, we present a strategy for capturing enveloped viruses on affinity grids (AG) for use in both conventional EM and cryo-EM/ET applications. We examined the utility of AG for the selective capture of human immunodeficiency virus virus-like particles, influenza A, and measles virus. We applied nickel-nitrilotriacetic acid lipid layers in combination with molecular adaptors to selectively adhere the viruses to the AG surface. This further development of the AG method may prove essential for the gentle and selective purification of enveloped viruses directly onto EM grids for ultrastructural analyses.
In this study, silicon nanowire (SiNW)/polycaprolactone composites with different surface topographies were fabricated by straightforward embedding or printing methods and their cytocompatibility was evaluated with a bone-relevant cell line derived from mouse stroma. The incorporation of biocompatible polymers with semiconducting SiNWs can ideally provide an enhanced environment to support proliferation and differentiation functions of bone cells. Cell/composite interactions were assessed with suitable assays including viability and alkaline phosphatase activity, while scanning electron microscopy characterization was used to study the morphology of cells grown on composites. Such results suggest that for nanowires in a vertical array, the presence of the polymer improves cellular attachment and overall viability relative to the nanowire-only system.
Contaminated water is one of the main sources of norovirus (NoV) gastroenteritis outbreaks globally. Waterborne NoV outbreaks are infrequently attributed to GII.4 NoV. In September 2009, a NoV outbreak affected a small school in Guangdong Province, China. Epidemiological investigations indicated that household use water, supplied by a well, was the probable source (relative risk 1·9). NoV nucleic acid material in concentrated well-water samples was detected using real-time RT–PCR. Nucleotide sequences of NoV extracted from diarrhoea and well-water specimens were identical and had the greatest sequence identity to corresponding sequences from the epidemic strain GII.4-2006b. Our report documents the first laboratory-confirmed waterborne outbreak caused by GII.4 NoV genotype in China. Our investigations indicate that well water, intended exclusively for household use but not for consumption, caused this outbreak. The results of this report serve as a reminder that private well water intended for household use should be tested for NoV.
An attenuated strain of Salmonella typhimurium has been used as a carrier for oral and intranasal genetic immunization. Here, we evaluate the efficacy of a vaccine strain of S. typhimurium. CSO22 (pGM-CSF/SS, plasmid granulocyte-macrophage colony-stimulating factor/somatostatin) expressing two copies of SS genes. A total of 115 piglets, aged 2 months old, were either orally or intranasally immunized against the vaccine strain CSO22 (pGM-CSF/SS) with three dosages (5 × 1010 colony forming units (CFU), 5 × 109 CFU and 5 × 108 CFU). For oral immunization, the specific anti-SS antibodies were detected in the immunized piglets. The levels of SS antibodies in the high-dose immunized group (5 × 1010 CFU) were significantly higher than that in the phosphate buffered saline immunized group (P < 0.01) and 40% of animals were positive in SS antibodies in the high-dose immunized group. Moreover, the weight gain of the high-dose group was increased by 20.86%, 10.26% and 15.30% during 4, 8 and 12 weeks, respectively, after immunization in comparison to the control. For intranasal immunization, the growth of the low-dose group was increased by 10.23% in the whole test period (12 weeks). In conclusion, our results suggest that the recombinant strain could elicit anti-SS antibodies and improve the growth performance of immunized piglets, and that the oral immunization program is better than the intranasal program.
The amplification of fast extraordinary mode waves with frequencies very close to the electron cyclotron frequency is investigated for a plasma which consists of a weakly relativistic electron component with a loss-cone type distribution and a cold background electron component. The basic mechanism of the amplification is attributed to a relativistic cyclotron resonance between the wave and the energetic electrons. The method employed in the present analysis enables us to solve the dispersion relation in a self-consistent manner for arbitrary ratio of the densities of the energetic and background electrons. It is found that the maximum growth rates occur at certain values of ω2pe/Ω2e and the angular dependence of the growth rate is sensitive to the ratios ω2pe/Ω2e and ne/nb. Here ωpe and Ωe are the electron plasma frequency and the electron cyclotron frequency, respectively, and ne and nb denote the number densities of the energetic and background electrons, respectively.
N-polar and Ga-polar GaN grown on c-plane sapphire by a metal-organic chemical vapor deposition (MOCVD) system were used to fabricate platinum deposited Schottky contacts for hydrogen sensing at room temperature. Wurtzite GaN is a polar material. Along the c-axis, there are N-face (N-polar) or Ga-face (Ga-polar) orientations on the GaN surface. The Ohmic contacts were formed by lift-off of e-beam deposited Ti (200 Å)/Al (1000 Å)/Ni (400 Å)/Au (1200 Å). The contacts were annealed at 850°C for 45 s under a flowing N2 ambient. Isolation was achieved with 2000 Å plasma enhanced chemical vapor deposited SiNx formed at 300°C. A 100 Å of Pt was deposited by e-beam evaporation to form Schottky contacts. After exposure to hydrogen, Ga-polar GaN Schottky showed 10% of current change, while the N-polar GaN Schottky contacts became fully Ohmic. The N-polar GaN Schottky diodes showed stronger and faster response to 4% hydrogen than that of Ga-polar GaN Schottky diodes. The abrupt current increase from N-polar GaN Schottky exposure to hydrogen was attributed to the high reactivity of the N-face surface termination. The surface termination dominates the sensitivity and response time of the hydrogen sensors made of GaN Schottky diodes. Current-voltage characteristics and the real-time detection of the sensor for hydrogen were investigated. These results demonstrate that the surface termination is crucial in the performance of hydrogen sensors made of GaN Schottky diodes.
AlGaN/GaN high electron mobility transistors (HEMTs) with a polarized Polyvinylidene difluoride (PVDF) film coated on the gate area exhibited significant changes in channel conductance upon exposure to different ambient pressures. The PVDF thin film was deposited on the gate region with an inkjet plotter. Next, the PDVF film was polarized with an electrode located 2 mm above the PVDF film at a bias voltage of 10 kV and 70 °C. Variations in ambient pressure induced changes in the charge in the polarized PVDF, leading to a change of surface charges on the gate region of the HEMT. Changes in the gate charge were amplified through the modulation of the drain current in the HEMT. By reversing the polarity of the polarized PVDF film, the drain current dependence on the pressure could be reversed. Our results indicate that HEMTs have potential for use as pressure sensors.
The potential use of carbon nanotubes (CNT) as interconnects requires also new characterization approaches as the existing ones are optimized for three-dimensional materials and do not work for inherently one-dimensional structures like CNTs. Therefore, we have developed a so-called pick-and-place process which allows to remove an individual CNT from a specific site and to place it at another location for further analysis. The approach is based on nanomanipulation combined with scanning electron microscopy (SEM). This paper presents the pick-and-place concept and explains the different steps required for its successful application. We further demonstrate its power by characterizing individual CNTs using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The developed pick-and-place approach overcomes the challenge of site-specific analysis of CNT interconnects and strongly facilitates the routine analysis of CNTs.
The behavior of a coil with ferrite core applied with an ac current and
under a magnetic field has been investigated. The field-induced changes of
both inductance and impedance have been observed. Based on this, a device
for electric current monitoring with the coil has been developed. The result
has shown that such a device is very sensitive and high efficiency, and
convenient to use in the field of power transmission and management.
The national high magnetic field laboratory builds and uses various high
field magnets for fundamental research. In building high field magnets, a
variety of high strength composites are required because of the Lorentz
stresses generated by high field exceeding the strength of most of the
materials, particular conductors. For example, a field of 60 T can generate
a magnetic pressure that corresponds to a stress in the conductor of 1.5
GPa, which is at the limit of known conducting materials with conductivity
higher than 70% International Annealed Copper Standard and sizes suitable
for building high field magnets. The design of high field magnets is limited
by these forces and, consequently, by the available materials. At the same
time, the materials need to have excellent physical properties. For
instance, the conductors need to have high electrical conductivity and high
specific heat and the superconductors should have high critical current in
field and low alternative current losses. This paper outlines our
requirements and research on metal matrix composite materials for building
high field magnets. The discussions include both the macrocomposite and
microcomposite. The scales of the structures in the composites are from
millimeters to nanometers.